Fig. 6.

Repolarizing I_K is reduced in right atrial myocytes in Akita mice. (A) Representative I_K recordings in right atrial myocytes isolated from wild-type (WT) and Akita mice. The recordings on the left represent total I_K measured between −100 and +80 mV. The recordings on the right represent I_K measured between −100 and +80 mV following a prepulse to −40 mV to inactivate I_to. Cell capacitances for these representative recordings were 33 pF for the WT and 38 pF for Akita. (B) Summary I_K IV curves measured at the peak of the I_K recordings without the prepulse (recordings on the left in A) for right atrial myocytes isolated from WT and Akita mice. (C) Summary I_K IV curves measured at the peak of the I_K recordings with the prepulse (recordings on the right in A) for right atrial myocytes isolated from WT and Akita mice. *P $<$ 0.05 vs. the WT at each membrane potential by two-way repeated measures ANOVA with Tukey’s post hoc test. (D) Summary I_K IV curves for the difference current between B and C, which is a measure of I_to. P = 0.85 for I_to density between the WT and Akita by two-way repeated measures ANOVA. For B–D, n = 19 WT and 16 Akita right atrial myocytes. (E) Representative I_K recordings at +30 mV illustrating the effects of 4-AP (100 $\mathrm{\mu }$M), which inhibits K_v1.5-mediated I_K, in right atrial myocytes from WT and Akita mice. (F) Summary data illustrating the amplitude of the 4-AP–sensitive I_K in right atrial myocytes from WT and Akita mice. n = 9 WT and 10 Akita right atrial myocytes. *P $<$ 0.05 vs. the WT by Student’s t test. Current densities are measured in picoamperes/picofarad (pA/pF).